In recent years, mobile reproducing devices, e.g., MP3 player, CD player and etc., have become quite popular and used widely. However, since available electric power for the mobile playback devices is restricted, various attempts to reduce power consumption for reproducing multimedia data have been tried. The method for reducing the power consumption and the problems of the conventional reproducing method will be explained below with reference to the drawings.
FIG. 1 is a block diagram showing the conventional method for reproducing data. Referring to FIG. 1, a reading part 110 reads data from a storage medium 100, e.g., optical disk, hard disk and etc., and an output part 120 reproduces the data. The data size read by the reading part 110 is decided by the performance of the mobile reproducing device. Also, the data size outputted by the output part 120 is decided by a playback rate. However, a problem arises because the data size read by the reading part 110 is greater than the data size outputted by the output part 120. Therefore, a buffer 115 is required to solve the problem based on the difference between the two numbers of data blocks. Also, the data is outputted from the buffer 115 regularly and stably, while the data read by reading part 110 may be irregular.
After the reading part 110 sends data to the buffer 115, the data reproducing method according to the conventional method continues to consume power because the spindle is still rotating at the full speed while the data filled in the buffer 115 are outputted.
Various approaches for solving the above-mentioned problems have been developed up to now. A typical approach to reduce the power consumption for a hard disk drive is to shutdown the disk when there are no outstanding I/O requests. That is, if no I/O requests are received during a predetermined time-out period of time, the reading part 110 reverts to stand-by mode in order to reduce power consumption.
However, in real-time playback, the effectiveness of the conventional power consumption reduction method by the time-out period of time is quite limited. Hereinafter, other problems according to the conventional power consumption reduction method will be described with reference to FIG. 2.
FIG. 2 is a schematic diagram showing the power consumption of a data read operation according to the conventional reproducing method.
The processing procedure of the reading part 110 includes a start-up mode 200, active mode 210, finish mode 220, and stand-by mode 230. The active mode 210 consists of read mode 203 and idle mode 206. Most of the power consumption occurs in the active mode 210.
The reading part 110 of the mobile reproducing device is initially in the stand-by mode 230. Although in the stand-by mode, the process moves into the start-up mode 200 when the I/O requests are received. The start-up mode 200 includes spin up, focus, and tracking as a preceding operation for retrieving data.
Further, the reading part 110 sends the data read from a disk to the buffer 115 in read mode 203, and then changes from the read mode 203 to idle mode 206. In the idle mode 203 where the reading part 110 waits until the predetermined data size from those data blocks filled in the buffer 115 are outputted through the output part 120, the disk head is in the parking position and the spindle is still rotating at the full speed.
If no request is received for a time-out period of time, the reading part 110 goes into finish mode 220 causing the platter to spin down and eventually going into stand-by mode 230. In the stand-by mode 230, the disk head is in the parking position and the spindle stops rotating.
However, because I/O requests are received during the time-out period of time according to the current reproducing device, power consumption is maintained in an active mode 210 until all data in a disk are read by the reading part 110 and outputted by the output part 120.
As mentioned above, the current data reading method goes into standby mode 230 if no I/O requests are received in the time-out period of time. Overhead regarding power consumption occurs in the idle mode 206 because most of the power consumption is done in active mode 210. Still, a method for minimizing power consumption is required because the size of the buffer is limited.
FIG. 3A is a graph showing the power consumption profile for an entire playback time period according to the conventional reproducing device, FIG. 3B is a graph showing the power consumption profile for start-up mode 200, and FIG. 3C is a graph showing the power consumption profile for finish mode 220.
FIG. 3A is a graph for showing the power consumption profile measured by an experiment. Also the playback duration of time consists of the startup mode 300, active mode 310, and finish mode 320.
The active mode 310 consists of a read mode 203 and an idle mode 206 according to the conventional reproducing method. Also, referring to FIG. 3A, there is little difference between the power consumption in the read mode 203 and the power consumption in idle mode 206. Therefore, the conventional power saving method is not effective.
Also, the conventional method (i.e., disk shut-down method) for minimizing power consumption by establishing a time-out period of time has a problem that the disk has to be rotating until all data in the disk are outputted if I/O requests are received. That is, until all data filled in the buffer 115 are outputted, the disk has to be rotating continuously in the idle mode 206 when the reading process is not executed. Therefore, unnecessary power consumption occurs.
As mentioned above, according to the conventional reproducing method, the conventional data reproducing device reproduces data filled in a buffer after it fills data in its buffer regardless of allotted buffer size and data size. Thereafter the process of filling the next data in the buffer and reproducing the next data is repeated whenever the buffer becomes empty. Accordingly, unnecessary power consumption occurs while data filling in the buffer are reproduced because the spindle is still rotating at the full speed during that period.